Sunday, 30 May 2010

The Black-Tailed Godwit (Limosa limosa) is an exceptional breeder in Extremadura (only one known case), a rare winter visitor, common on spring passage (30,000 birds) and rare on post-breeding migration. The region is recording an upward trend of birds on passage even though Europe as a whole has recorded a “moderate decline” with a 40% drop in the eight-year period running from 1999 to 2006 (PECBMS, 2009). It is listed as Near Threatened in the 2010 IUCN Red List Category.

The post-breeding congregations in the stubble-free flooded ricefields of Vegas del Guadiana is a fairly recent phenomenon. In the mid 1980s the species made no stopovers in Extremadura; numbers had built up to about 4000 by 1990 and it was not until the start of the C21st that numbers settled down at over 25,000 birds. In recent years the flock sizes within the Vegas Altas area have dropped in the east (Palazuelo-Madrigalejo) and increased in the west (Santa Amalia, Hernán Cortés and Yelbes), where they have been most abundant in the 2004-2007 period. There are other minor, more sporadic flocking areas in Vegas Bajas, La Albuera, Llanos de Cáceres and Vegas del Alagón (Masero et al., 2008).

The population in the Vegas del Guadiana has been closely studied in the 2004-2007 period by the Conservation Research Group of Extremadura University (GIC-UEX in Spanish initials), colour ringing 341 birds. From plumage details 8% of them were identified as L.l. islandica, a race that mixes with the dominant L.l. limosa and is observed in the same spots and on the same dates. Ringed birds seen in Extremadura came from Holland (86%, limosa race), Iceland and UK (10% and 4% respectively, islandica race). Birds ringed in Extremadura, for their part, have been spotted in Iceland (3%, islandica race), Holland (70%), France (13%), Germany (6%), Belgium (6%) and Denmark (2%); 97%, therefore, in zones of the limosa race. The return rate (ringed birds returning in latter seasons) is estimated to be 36%, with movements about the Iberian peninsula being noted: 6% of Extremadura-ringed birds are seen in Portugal, even in the same season, and 31% of Cádiz-ringed birds are seen in Extremadura in the same year or following years (Masero et al., 2009).

To find out the length of stay 24 birds were caught and radiomarked in 2004. Two waves of incoming migration were detected, the first around 20 January (17 January in 2004) and the second around 10 February (7 February in 2004). The birds of the first incoming wave were still in winter plumage and hardly moulted at all into summer plumage during their Extremadura stay, even though the stay was longer (minimum estimate of 40 days) and their departure later (1 March on average). Over sixty percent of the birds of the second wave arrived in summer plumage, staying for a shorter time (minimum stay of 17 days) and left one week earlier (24 February on average). The average stay for the whole set of birds under study was 22 days, all of them having left by 15 March. The stopover time on spring passage is deemed to be a key factor in the success rate of the following breeding season.

The simultaneous counts carried out in the Vegas del Guadiana, displayed on a graph, peak steeply, then falling away gently before a sharp drop in February (varying between the first and last week of the month in different years). The average maximum count is 24,200 with an all-time high of 27,643 on 07/02/04; this represents at least 15% of the migratory population on the East Atlantic route. A comparison with other spots on the Iberian Peninsula shows that Doñana records highs of up to 48,000 birds, usually peaking earlier than in Extremadura (December in 2002-2006; January in 1999-2001), while the Portuguese estuaries of the Tagus and Sado rivers show a similar pattern to Extremadura, with February highs (e.g. 44,700 birds in February 2006). Other important Iberian stopover points are Bahía de Cádiz and Marismas del Odiel in Spain and Ría Formosa, Castro Marim and Ría de Aveiro in Portugal. Recent decades have recorded a big increase in the number of Black-Tailed Godwits in Extremadura and Doñana, offsetting the declining numbers in traditional stopover points in Northwest Africa. Taken as a whole, Southwest Iberia plays a functional role in the spring migration of Black-Tailed Godwits (Masero et al., 2010), merging into the end of the wintering phase.

Sunday, 23 May 2010

The 2008 national Griffon Vulture (Gyps fulvus) census recorded 1570 breeding pairs in Extremadura, with a more realistic estimate of 1943 pairs spread out around 198 different sites: 156 colonies and 42 isolated pairs. Spain’s total Griffon population was reckoned to be about 25,000 pairs in 2008, with an educated guess of 30,000 pairs and a total population of 75,000 to 100,000 birds; this means that Extremadura ranks sixth among Spanish regions, accounting for about 6.3% of the total.

Broken down by provinces Cáceres weighs in with 1361-1743 pairs, nearly 90% of the region’s total and 5.5% of Spain’s. This makes it the 8th ranking province in terms of its Griffon population and 14th in density (8.8 pp/100 km2). Extremadura’s other province, Badajoz, is home to 199-200 pairs, 0.8% of Spain’s total, making it the 22nd province in terms of population and the 28th in terms of density (0.9 pp/100 km2). Pride of place in Cáceres goes to the River Tagus and the final runs of its tributaries Tiétar, Alagón, Almonte, Erjas, Salor and Aurela. Most important amongst the mountainous areas are Ibores-Villuercas in the south east and, some way behind, Las Hurdes and Gredos in the north, together with some sierras of the extreme southwest. In the province of Badajoz Griffons breed in three sectors: northwest (Alburquerque), centre and northeast (La Siberia and La Serena). By far the most important area of all is Monfragüe, boasting 650-800 pairs, 42% of Extremadura’s population, nearly all of them in the 18,000 hectares of the National Park.

Alongside the census, breeding success was also monitored in 526 pairs, one third of the total population found, with an average of 4.2 visits. The results of this survey were: productivity 0.58 and breeding success rate 0.63; slightly lower than the figures for Spain as a whole, with a productivity of 0.62 and breeding success rate of 0.67. This figures are 12% down on 1999, although the average number of visits back then was only 2.3, so in all likelihood they were overestimated. Although the breeding success rate was nearly the same in both of Extremadura’s two provinces, productivity differed, with figures of 0.61 in Cáceres and 0.54 in Badajoz. One possible reason for this difference is the higher proportion of nonbreeding pairs detected in Badajoz (13%) in comparison to Cáceres (5%), as well as a higher number of visits in Badajoz (5 against 3.8 in Cáceres).

As for the population trend, this has always been steadily upwards since the very first national census in 1979. In this 30-year period the figure has quadrupled, with a 40% rise from 1999 to 2008, an increase of under 55% from 1979 to 1989 and 88% from 1989 to 1999. No real changes were appreciated in the breeding range from 1999 to 2008, although new colonies were occupied within and on the edge of the known range. The number of new sites occupied was 39 (up 24%), mainly small colonies and isolated pairs. The increase is therefore due above all to the growth of existing colonies. By way of comparison the increase in Spain as a whole was 58% from 1999 to 2008.

Sunday, 16 May 2010

A Pied-Billed Grebe (Podilymbus podiceps), only four official records for Spain (1984-2007), has turned up on a pond near Trujillo in Extremadura. First news came on 13 May 2010 and the last sighting came on the 15 May. Photo by Nigel Milbourne (Website: www.blagdonlakebirds.com)

Saturday, 15 May 2010

The Spoonbill Monitoring Group (Grupo de seguimiento de espátula común: GRUSEC) has published an article on breeding Spoonbills (Platalea leucorodia) in Spain on their blog. We invite you to drop in and read it here. The map below shows the breeding sites in Extremadura up to 2010, with 14 known sites, some very close to each other so the total number is probably nearer 10.

The graph, taken from GRUSEC, shows the regional trend, with an all-time high in 2009 and a dip in 2010 (provisional figures), partly because of high rainfall flooding out nest sites.

Wednesday, 12 May 2010

The Spanish Bird Common Survey scheme called Common Breeding Bird Monitoring Programme (seguimiento de aves communes reproducturas en España: SACRE) has thrown up figures on the commonest birds in Extremadura and we show below the ranking with the 20 commonest (individuals).

By way of comparison we also show the ranking of the 20 commonest breeding species in the whole of Spain, with many similarities (House Sparrow and Starling topping both lists) and some high-ranking idiosyncrasies of Extremadura (for example Azure Winged Magpie and Spanish Sparrow).

Tuesday, 11 May 2010

Winter is without doubt one of the best birdwatching times in Extremadura, with the thousands-strong flocks of Cranes joined by many other visitors from northern climes. Until now there has been no way of monitoring the distribution of these wintering birds, until the SEO recently published the partial results of the Atlas of Wintering Birds in Spain. The image below (species-rich areas in red and species-poor in blue) shows that Extremadura as a whole and the province of Cáceres in particular is one of the richest areas for wintering birds in the whole of Spain. It should be stressed that these results are still provisional.

Sunday, 9 May 2010

The blog of the local birdwatching group (grupo local SEO-Cáceres, Spanish Ornithological Society in Extremadura) came on line last May. Its remit was to deal with the more bureaucratic aspects of the local group, such as organising projects, announcing matters of interest and various calls for information and help. It was thought that the more purely birdwatching aspects of the group would be best dealt with elsewhere: hence the birth of this new blog, which aims to appeal to a wider public by giving the breaking news on Extremadura’s birdlife and nature as a whole.